Much of what we need to plan for our survival is already known, but what we know, how we know, and who knows is divided up between disciplines. Thus much of the problem of ensuring our survival is a matter of learning across the disciplines. We identify four modes through which we bring disciplinary knowledge together: the unity of science, integrated assessment, heuristic models, and distributed learning networks. Although none of them are perfect, we can learn how to put our knowledge together across the disciplines much better than we do.